1. Technical Field
The present disclosure relates to systems for electric power generation, storage and distribution.
2. Description of Related Art
Current electric power generation and distribution is centralized. As such, large scale power generation and distribution lacks flexibility, resilience and is vulnerable to large scale blackouts and catastrophic regional emergences. These issues are recognized globally. Currently many governments (US, Japan, EU, etc.) are sponsoring long-term efforts to resolve these type of issues. The “centralized approach” is also very inefficient and costly, and hence not feasible, when it comes to energy generation and storage due to lack of a mature and cost effective technology for large scale applications. A key element in all possible solutions lies in the energy storage. Current storage technologies have limited application to electrical grid system storage because of their power limitations, low energy density, and high cost.
Issues of integrated electric power systems and generation, and electrical battery current regulation systems are known and described, for example, in U.S. Pat. No. 5,764,502 and U.S. Pat. No. 7,589,498 B2. One of the oldest types of storage makes use of the lead acid battery technology. While it is used predominantly for cars, this technology is still evolving and continues to be used in a number of energy storage projects in the United States. Although lead acid battery technology has many advantages, its energy management capabilities are very limited due to a short life cycle, inconsistent energy delivery, and high maintenance cost.
A promising candidate for large scale energy storage applications is the sodium-sulfur battery technology which has been tested for electrical grid applications by, for example, the US Department of Energy. This battery has relatively higher power, energy density, and efficiency. However, it is not feasible for residential and commercial applications due to: (1) operational, safety, and maintenance requirements (operates at high temperatures about 300° C.); (2) high cost ($3,000 per kilowatt installed); and (3) the large amount of space it requires. By some estimates a 20 kW system may require a 30 square foot space. Therefore the application of known methods and systems is heretofore recognized as being limited and not applicable to residential/commercial use. (As used herein, “residential/commercial” means “residential and/or commercial.”).